Keytruda, a medication developed by Merck & Co., was first approved by the U.S. Food and Drug Administration (FDA) for cancer treatment in 2014. Specifically, it was approved for the treatment of advanced melanoma in patients whose disease had progressed after other treatments [1].

Keytruda, also known as pembrolizumab, is a type of drug known as an immune checkpoint inhibitor. It works by blocking a protein called PD-1, which helps to keep the immune system from attacking cancer cells [2].

It is worth noting that Keytruda has since been approved for the treatment of several other types of cancer, including certain types of lung, head and neck, and Hodgkin lymphoma [3].

Sources:

* [1] "FDA approves new indication for Keytruda." FDA. <https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-new-indication-keytruda>.
* [2] "Keytruda." National Cancer Institute. <https://www.cancer.gov/about-cancer/treatment/drugs/keytruda>.
* [3] "Keytruda (pembrolizumab) for Cancer." DrugPatentWatch.com. <https://www.drugpatentwatch.com/drugs/keytruda>.